Acoustical device



June 24, 1930. R. T. CLOUD ACOUST ICAL DEVICE 2 Shets-Sheet 1 Filed March 19, l928 June 24, 1930. RT L D 1,761,211?

ACOUSTIGAL DEVICE Filed March .19, 1928 2 Sheets-Sheet 2 SM I fi g- 6 5 Patented June 24, 1930 UNITED STATES PATENT OFFICE RAYMOND 'r. CLOUD, or CHICAGO, ILLINOIS, ,ASSIGNOR 'ro oncn'nsrrnarnoun com:-

I'ANY, or CHICAGO, ILLINOIS, A ooRronArIoN or DELAWARE ACOUSTICAL DEVICE Application filed March 19, 1928. Serial No. 262,633.

. This invention pertains to acoustical devices, and more particularly to improvements in electrical sound reproducers especially adapted for use in electrical pick-ups .cooperable with phonograph records and the like.

,One of the objects of my invention is to provide an improved electrical reproducer of a highly simple nature and inexpensive construction, and of such a design that it may be employed With advantage in a phonograph reproduction unit.

Another object of the invention resides in the provision of an improved phonograph transmitter for reproducing sound vibrations from a grooved record.

It is well known that perfect electrical reproduction of a sound record is possible only when the vibrations of the armature follow precisely the vibrations transmitted thereto by the vibratory reed or the like. In other words, there must be no tendency for the armature to vibrate after the vibrations transmitted thereto have ceased, i. e. the armature and its associated parts of the vibratory system including the stylus must be dead beat.

At present, it is standard practice to employ a damping material in connection with the vibratory system of a phonograph transmitter and the like to aid the system in vibrating as a unit and for limiting the vibration frequencies to a predetermined range, so that distorting vibrations are re duced to a minimum. Rubber is at present universally used for this purpose.

It is also well known that the biggest drawback in connection with the use of rubher as a damping medium is that it loses its elasticity and deteriorates so rapidly that its useful life in any instrument is limited. In fact, I find that the use of rubber as a damping element in phonograph transmitters necessitates frequent replacements which add considerable to the upkeep and maintenance of a phonograph reproducing system.

From experimentation in connection with damping materials and the reproduction of sound waves, I have discovered. a substitute for the conventional rubber damping material which has far better damping qualities and much greater longevity than rubber. The form of this material with which I have attained excellent results is none other than the well-known printers roll or roller composition. This composition has the requisite kineomatic viscosity and elastic qualities, and the amount or mass of it required for the damping of a stylus bar or vibratory system is relatively small.

At present, it is known that certain liquids are better damping mediums than rubber. Obviously, it would not be practical to use liquid as a damping material in an instrument such as that under discussion inasmuch as the allotted space is limited andv also in View of the fact that it is practically impossible to provide means for maintaining the liquid in cooperation with the vibratory system in such a manner as to prevent leakage.

I have conducted extensive experiments in connection with the use of this printers roll as a damping material and have found that due to the fact that it has relatively great iterative impedance, or in other words radiation resistance, a relatively small amount of it will provide ample damping material for a vibratory system such as that employed in a phonograph electric transmitter, so that there are no reverberations. Then, too, experiments have disclosed to me that a given wave motion imparted to this material will completely die out in a comparatively small amount of the material. I attribute this to an inherent latent quality in this composition which I term a high attenuation constant.

It has also been my observation from experiments in which: I have used this damping material in connection with an electrical pick-up of the character above mentioned that the inertia of the molecules com- I posing this damping medium is so great that the material is compressed a relatively large amount by the minute vibrations to which it is subjected by the armature. That is to say, a wave motion imparted to this damping material by the vibrating armature is ment, namely the one in which rapidly attenuated due to the relatively great friction of the particles set into motion in this material, and as a result the wave motion does not travel far into the material. In fact, I have found that any wave motion imparted to one side of this dampin medium by the vibrating element is compI tion can reach the other side of the damping medium. Moreover, this damping material is of such a nature that it does not radiate any waves, and hence there are no reverberations which would be detrimental to the proper action of the vibratory armature.

I have also discovered that this damping material need only be stuck to the vibratory element or armature. That is to say, it does not require any additional means in order to enable it to properly serve as a damping medium for the armature. :Whether it is connected to other means than the armature is optional. In the drawings it will be noted that I have illustrated both arrangements. The former arrangethe damping medium is only connected to the vibratory element or armature, clearly indicates that the damping action of this material is not one involving merely the compressing and flexing of the material such as is the case in the conventional damping medium of rubber, but apparently involves an inertia action on the part of the molecules or particles of matter composing this damping medium. In other Words, the damping medium has an inherent or latent kineomatic quality, which might properly be called kineomatic viscosity, and which is of such a nature that a relatively small amount of the material by itself attenuates and absorbs wave motions.

Moreover, I have found that printers roll has a higher ratio of kineomatic viscosity to mass and elasticity than any other material whichI have experimented with. Of course, it will be appreciated that although I have attained excellent results with printers roll as a damping material, the invention is not to be thus limited for obviously there are a number of other materials available which have qualities approximating the, kineomatic and physical qualities of printers roll. My use of printers roll has also been influenced to a considerable extent by the fact that it is already a commercial product and is readily obtainable in a condition ready for use in instruments of the class to which my invention pertains. Then too printers roll can readily be melted and poured into the spaces provided.

- It will be evident from the foregoing that another object of this invention is to provide anew damping material having far superior qualities than rubber for use in etely absorbed before the wave mosupporting instruments and present character a vibratory system wherein the parts thereof are so connected together that the inertia thereof is materially less than that of analogous conventional vibratory systems, and so that the elasticity and sensitiveness of the system is greatly enhanced.

Still another object of this invention is the provision of a reproducing instrument including a vibratory system so arranged that all of the vibrating parts may be welded together, thereby reducing the inertia of the system to a minimum and augmenting the natural flexibility of the system.

In accordance with the general features of the present invention, I provide an acoustical device capable for use as a phonograph transmitter comprising a frame, magnetic coils disposed within the dimensions of the frame, a stylus pivotally connected to the frame for actuating the armature associated with the coils, and a resilient connection between the stylus of the armature, a torsional pivot pin connected to the armature having a relatively high resistance to rotary movement as compared with the inertia of the armature and a damping-material for the armature of such kineomatic qualities that it affords considerable resistance to the transmission of wave motion, of the character to Which the armature is subjected, therethrough.

Another feature of the invention resides in the provision of a novel frictional mounting for each of the ends of the torsional pivot pin of the device of my invention adapted to frictionally bind and wedge each of the ends of the pin to the frame, whereby the pin is held against rotary movement.

Other objects and advantages of my invention will more fully appear from the following detail description taken in connection With the accompanying drawings which illustrate several embodiments thereof and in which: 1

Figure 1 is a plan view of a phonograph transmitter embodying the features of this invention;

Figure 2 is a side view of the transmitter shown in Figure 1;

Figure 3 is a cross-sectional view taken on substantially the line IIIIII of Figure 1 looking upwardly;

Figure 4 is a vertical sectional View taken on substantially the line IV-IV of Figure I 1 looking in the direction indicated by the the construction of the connection between the stylus and the armature, the damping material being omitted for sake of clearness;

Figure 6 is a plan view of an alternative form of my invention, the base plate and electromagnetic coils being omitted;

Fi ure 7 is a sectional view taken on substantially the line VII-VII of Figure 6 looking downwardly;

Figure 8 is a vertical sectional view drawn to an enlarged scale and taken on substantially the line VIIIVIII of Figure 6 looking in the direction indicated by the arrows;

Figure 9 is a fragmentary sectional view, partly in elevation, drawn to an enlarged scale and illustrating in detail the construction of the connection between the armature and the stylus, and

Figure 10 is a fragmentary detail View, partly in section and elevation, drawn to an enlarged scale and taken on substantially the line XX of Figure 6 illustrating the frictional mounting for an end of the torsional pin.

In the drawings:

Like reference characters designate similar parts throughout the several views. The reference character 10 designates generally an annular frame member having a central rectangular opening 11 into which the upper ends of a pair of electromagnetic coils 12 extend. The other ends of the coils 12 are mounted on a base plate 13 connected to and spaced from the frame member 10 by means of bolts and nuts 14. The windings of coils 12 are connected in series and have their external ends connected to terminal posts'15 and 16 secured to base plate 13. These posts may be connected to any con ventional electrical reproducing circuit.

Also mounted upon the base plate 13 is a U-shaped magnet 18 which is secured to the base plate by bolts 19. It will be noted that the two coils 12 are disposed between the legs of the magnet 18.

Positioned above the top of the pair of coils 12 is an armature 20, one end of which is secured to a torsional pivot pin 21, the function of which we shall describe more in detail hereinafter. This pin 21 extends clear across the rectangular opening 11 in frame member 10 and has its ends extending into aligned passageways 22 and 23 formed in the frame member. The ends of the pivot pin are held in place against movement by means of setscrews 24E threaded into the frame member so as to engage the associated ends of the torsional pin 21;

The other end of the armature 20 has fastened to it a substantially U-shaped element 25 having the free ends of its legs suitably anchored to the armature 20. The free ends of the U-shaped element 25 may be soldered or secured to the armature 20 by any suitable means. I preferably make this element 25 of a resilient material, such, for example, as music wire. The upper or loop end of the element 25 is rigidly secured to one end of a stylus bar 26 directly over the top of one of thecoils 12. This stylus bar 26 has formed integral with it between its ends a pair 'of diametrically op osed laterally extending bearing members 2 and '28 cooperable with trunnions 29 and 30 thus be evident that the stylus bar 26 is' pivotally mounted between its ends upon the top of the frame member 10. The other end of this lever or stylus bar 26 is provided with a socket 35 adapted to receive a phonograph needle or the like. Threaded into the socket end of the stylus bar 26 is an adjustable setscrew 36 adapted to hold the needle in the socket 35. Attention is directed to the fact that the stylus bar 26 is disposed in substantially a vertical position.

The vibratory system of this acoustical device including the armature 20, the U- shaped link 25, and a'portion .of the torsional pin 21 are covered by means of a small'amount of damping material, which material, as previously mentioned, may consist of printers roll or composition. Of course, it will be appreciated that there are a number of different kindsof printers roll or composition on the market. The form with which I have experimented is the product of the Rapid Roller Company of Chicago and is known as Rapid Special New Composition. I have designated this damping material by the reference character 40.

As far as I have been able" to ascertain, my invention can be carried out by the use of any of the available or market forms of printers roll composition. This composition is used in the manufacture of inking rollers. By inking roller, as defined in the 1914 edition of The Century Dictionary, I

mean, an elastic cylinder made of a composition of glue and molasses or of glue, glycerine and sugar cast in a mold around a spindle or stock for applying ink to type by being rolled over it.

I have attained excellent results with the above referred to rapid special new com position, which I have been informed is made entirely of new or fresh materials. In some of the commercial .forms of printers roll available on the market the composition is made in part from old composition stripped from worn out inking rollers and the like. Although my invention can be carried out with any of the commercial forms of printers roll composition, still I find that a composition made entirely from new materials is preferable for the reason that 1t appears to have more life and, hence, will hold up much longer in use.

I have been advised by the manufacturer of the above referred to Special New Composition that its constituents are roughly as follows: I

50 parts of high grade hide glue;

50 parts of glycerine;

35 parts or less of water;

5 parts of vegetable-oil; 2 parts of printers varnish.

In the appended claims, I have used the term printers roll, and by this term I mean any composition having the constituents and characteristics of the above discussed com positions employed in the manufacture of printers inking rollers.

This damping material has by far greater life than rubber,which is at present universally used for this purpose. I have built a number of electrical pick-ups using this material as a damping medium and have thus far experienced no difiiculty with this feature of those devices.

The wave motions imparted to this damping medium 40 by the oscillating armature 20 are of exceedingly small magnitude. Each oscillation of the armature sets up a wave motion in the medium 40. I have found that due to the fact that this medium has a higher ratio of kineomatic viscosity to mass and elasticity than rubber or any other analogous damping substances results in the wave be ing attenuated within the damping medium.-

In other words, even though only a relatively small amount of this damping medium 40 is used, the infinitely small wave motions to which it is subjected are completely absorbed within the medium, so that it is impossible for them to pass therethrough. As previously mentioned, I attribute this characteristic of the damping medium 40 to the fact that it has a high attenuation constant when compared with rubber and such substances.

It also appears from my experimentations that this damping medium has what might be termed relatively great iterative impedance or in other words rediat-ion resistance and as a result of this characteristic a comparatively small amount of the medium 40 will insure ample damping for the vibratory system associated therewith, whereby no reverberations are set up by the wave motions imparted to the medium 40.

The operation of this form of my novel phonograph transmitter is briefly as follows:

Movements imparted to the stylus bar 26 by its needle engaging a grooved record (not shown) are imparted to the armature 20 through the resilient U-shaped connection 25. Due to the inelastic quality of connection 25 under normal conditions, even the slightest degree of movement imparted to stylus bar 26 will be imparted to armature 20. Then, too, by locating the lever or stylus bar 26 substantially centrally of the U- shaped connection 25 and by extending the stylus bar across the axis of the connection 25, the inertia of this portion of the lever system comprisin the connection and the bar 26 is substantially reduced.

Attention is also directed to the fact that as long as the stylus bar 26 is vibrated in a i. direction at right angles to the plane .of

armature 20 and in a direction parallel to the axis of the connection 25, the wire connection 25 will be relatively inelastic and will not be buckled or flexed to any considerable extent by the stresses imparted thereto. However, inthe event that the stylus bar 26 is caused to oscillate in a direction at right angles to the travel of the record, these vibrations will produce stresses disposed at right angles to the axis of the U-shaped connection 25 which flexes laterally or transversely to absorb these stresses, whereby they are not imparted to the armature 20. In other words, I provide means in the form of connection 25 for eliminating vibrations which do not comprise part of the recorded sound waves being reproduced. This, as is evident, will result in a substantial improvement in the tone quality of the sound waves electrically reproduced from the record.

The torsional pin 21 to which the armature 20 is fastened constitutes an ideal mounting for the armature, since it does not materially add to the mass of pin 21 and hence does not cause the pin to have as great an inertia as is usually present in the conventional'type of mounting for the armature. This torsional mounting also substantially prevents continuing of the vibrations imparted to the armature 20, thus enabling it to respond positively to the stresses imparted thereto by connection 25. It is, of course, to be understood that the torsional mounting for the armature 20 does not have a great enough torsional stiifness as to require an excessive movement of the stylus bar by the record groove, which feature would be detrimental in that it would result in excessive wear of the grooved record. Moreover, the torsional stiffness of pin 21 is such that together with the inelasticity of the wire connection 25, it will result in the entire system having a natural period of vibration. However, it is to be noted that this period of vibration has a substantial damping quality, so that in the event the .stylus bar 20 should be given a relatively great blow or impact, the vibration imparted to the system by the stylus bar would be of relatively short duration, whereby the tone and quality of the sound electrically reproduced would not be impaired.

The damping action of the medium 40 50 is adapted to be connected to a base plate (not shown) such as plate 13 shown in the other form of my invention, which plate as illustrated in Figure 3 carries the magnet and the electromagnetic coils. It will be noted that I have provided the frame member 50 with three openings 52 through which the bolts used to secure it to the base plate may extend.

Positioned directly in line with opening 51 is an armature 53 adapted to be asso-' ciated with the electromagnetic coils (not shown). This vibratory armature 53 is welded to an intermediate portion of a torsional pin 54 extending through the opening 51 and having its ends secured to the frame 50. Each end of this pin 54 extends into a -V-shaped slot 55 formed in the plate 50 and is adapted to be held in the V-shaped slot 50 through the means of a washer 56 secured to the frame by a bolt 57. This arrangement is such that when the washer is forced into tight engagement with the outer surface of the corresponding end of pin 54, it causes the end of the pin to be frictionally wedged to the frame 50. The two ends of the pin 54 securely wedged to the frame 50 enable the torsional pin 54 to be held against rotation.

Attention is directed to the fact that only one end of the armature 53 is welded to the torsional pin 54. The other end of the armature 53 has welded to it the ends of a looped and twisted music wire link 60. The loop portion of this link 60 extends over and is welded to one end of a lever or stylus member 61 pivotally carried between its ends by a pair of lugs 62 formed integral with the frame 50. The other end of the lever or stylus bar 61 is formed with a socket portion 63 for receiving a phonograph needle and also includes a setscrew 64 adapted to hold the needle in the socket 63 in a wellknown manner.

The armature 53 has secured to it a dab of damping material designated by the reference character 65. This material 65 is of the same composition as the damping medium 40 and may be applied to the armature by initially melting the composition and thereafter pouring it onto the armature. The natural adhesive qualities of this material cause it to stick to the side of the armature 53. Attention is directed to the fact that in this form of the invention the damping medium 65 is shown as being connected only to the armature. That is to say, it does not have any additional support or any connection whatsoever to the other mechanism associated with the armature. It is carried solely by the armature 53.

The operation of this alternative form of my invention is practically the same as that of the otherform previously described. It will be evident that vibrations imparted to the stylus bar 61 are transmitted to the armature 53 through the twisted and looped link 60. I have found that this type of link is slightly more advantageous than the link shown in Figure 5 in that it is relatively rigid and readily transmits the vi brations imparted thereto to the armature so that the armature and stylus bar oscillate as a unit. The operation of this link, however, is much the same as that of the link 25.

The welded connections between the link, the stylus bar 61, and the armature 53 reduce the overall mass of the vibratory system, thereby reducing the inertia of the system to a minimum and aiding materially the natural flexibility of this system.

The operation of the damping medium 65 shown in Figure 8 is substantially like that shown'in Figure 4, with the exception that it is only disposed in contact with the armature 53. The vibrations of the armature 53 when in operation set up wave mo-. tions which are attenuated and completely absorbed by the medium 65. This, damping action of the medium 65 is not dependent upon a compressing and fiexure of the medium. That is to say, in the conventional damping medium or rubber the rubber is usually disposed between the vibratory element and other means, whereby it is adapted to be stretched and compressed by the vibrations imparted thereto. This is not true of the medium 65 which depends for its damping qualities upon its inherent kineomatic characteristics previously described.

Now, of course, it is to be understood that although I have illustrated and described in detail the preferred forms ofmy invention, the invention is not to be thus limited, but only in'so far as defined by the scope and spirit of the appended claims.

I claim as my invention:

1. In combination, a vibratory element,

and a damping medium having the acoustiand a damping medium therefor comprising printers roll.

4. In combination, a vibratory element,

and a damping medium having the acoustical characteristics of printers roll composition therefor having a high attenuation constant as compared with its mass.

5. In combination, a vibratory element, and a damping medium having the acoustical characteristics of printers roll composition therefor having a high attenuation constant as compared with its mass and arranged to completely attenuate wave motions imparted thereto by the element.

6. In combination, a vibratory element, and a damping medium having the acoustical characteristics of printers roll composition therefor having relatively great iterative impedance as compared with its mass.

7. In combination, a vibratory element, and a damping medium having the acoustical characteristics of printers roll com osition, the molecules of which have relatively great viscosity as compared with the mass of the medium, said medium having such molecular construction that when the wave motions are imparted thereto by said element the friction of the molecules results in a complete attenuation of the wave transmitted to the medium.

' 8. An acoustic device comprising a frame, a vibratory element associated therewith, a torsional support for said element, means for vibrating the element, and a damping medium having the acoustical characteristics of printers roll composition connected to the element of such a composition as to completely absorb and attenuate an wave motions imparted thereto by the vi ratory element, said medium being composed of molecules having relatively great viscosity as compared with the mass of the medium.

9. An acoustic device comprising a frame, a vibratory armature associated therewith, means for vibrating the armature connected to the frame, and a damping medium having the acoustical characteristics of printers roll composition connected only to said armature and adapted to completely absorb wave motions imparted thereto by said armature.

10. An acoustic device comprising a frame, a vibratory armature associated therewith, means for vibrating the armature including a link and a stylus bar, said link being welded to said armature and to said bar, and a torsional mounting for said armature connected to said frame, said welded connections reducing the mass of the vibratory parts to a minimum.

11. An acoustic device comprising a frame, a vibratory armature associated therewith, means for vibrating the armature including a link and a stylus bar, said link being welded to said armature and to said bar,

a torsional mounting for said armature connected to said frame, said welded connections reducing the mass of the vibratory parts to a minimum, and a damping medium on said armature comprising printers roll composition.

12. An acoustic device comprising a frame, vibratory armature associated therewith, a torsion pin having said armature connected to an intermediate portion thereof, said pin having each of its ends extending into a V-shaped slot in said frame, and means for wedging the ends of the pin in said slots so as to rigidly secure the pin to .the frame and to prevent rotation of said pin and means for vibrating said armature including a stylus and a link connecting the stylus to the armature.

13. An acoustic device comprising a frame and a vibratory armature associated therewith, and means for vibrating the armature including a stylus bar connected to the frame and a link connecting the stylus bar to, said armature, said link comprising a twisted loop of wire.

14. An acoustic device comprising a phonograph transmitter including a supporting member movable relative to a phonograph record, a magnet carried by said supporting member, a coil associated with said magnet, an armature associated with said coil and mounted for rocking movement relative to said magnet, a torsional element connected to said supporting member and having said armature secured thereto, said armature and element being of relatively small mass, a stylus connected to said'armature,

and a damping medium for said armature comprising printers roll composition.

15. An acoustic device comprising a phonograph transmitter including a supporting ember movable relative to a phonograp record, a magnet carried by said supporting member, a coil associated with said magnet, an armature associated with said coil and mounted for rocking movement relative to said magnet, a torsional element connected to said supporting member and having said armature secured thereto, a vibratory stylus for engaging the phonograph record, a resilient connection between said armature and said stylus, and a damping medium for said armature comprising printers roll composition.

16. An acoustic device comprising a phonograph transmitter including a supporting member movable relative to a phonograph record, a magnet carried by said supporting member, a coil associated with said magnet, an armature associated with said coil and mounted for rocking movement relative to said magnet, a vibratory stylus for engaging the record, a resilient connection between said armature and said stylus, said connection being adapted to flex substantially in a transverse direction to that of the movement of said armature, and a damping medium for sa'id armature comprising printers roll composition.

17 An acoustic device comprising a phonograph transmitter including a support ing member movable .relative to a phonograph record, -a magnet carried by sa1d supporting member, a coil associated with saidmagnet, an armature associated with said coil and mounted for rocking movement relative to said magnet, a torsional element connected to said supporting member and having said armature secured thereto, said armature and element being of relatively small mass, a vibratory stylus for engaging the phonograph record, a wire connection between said armature and said stylus, said connection'being adapted to flex substantially only in a transverse direction to that of the movement of said armature.

18. An acoustic device comprising a phonograph transmitter including a supporting member movable relative to a phonograph record, a magnet carried by said supporting member, a coil'associated with sa1d magnet, an armature associated with said coil and mounted for rocking moveprising an electromagnet, a stylus bar associated with said electromagnet for cooperation therewith and damping" means forsaid bar comprising printers roll composition.

21. In combination, an acoustical vibratoryelement, means associated with said element for the reproduction of sound waves,

and a damping medium for said element consisting of printers roll composition. I

22. In combination, a vibratory stylus bar and damping means therefor comprising printers roll composition. I In testimony whereof I have hereunto subscribed my name at Chicago, Cook County, Illinois.

RAYMOND T. CLOUD.

ment relative to said magnet, a torsional element connected to said supporting member and having sa1d armature secured thereto, a vibratory stylus for en aging the phonograph record, said stylus eing pivotally connected to said supporting member in such a manner that one of its ends is disposed directly opposite to saidarmature and substantially parallel to said armature, a connection between said end of the stylus and said armature, and a damping medium for said armature comprising printers roll composition. 19. An acoustic device comprising a phonograph transmitter including a supportin member movable relative to a phonograp record, a magnet carried by sa1d supporting member, a coil associated with said magnet, an armature associated with said coil and mounted for rockin movement relative to said magnet, a torsional element connected to said supporting member and having said vibratory stylus for engaging the phonograph record, said stylus being pivotally connected to said supporting member m such a manner that one of its ends is disposed directly opposite to said armature and substantially parallel to said armature,

armature secured thereto, a

a connection between said end of the stylus y and said armature, sa1d connection comprising a wire adapted to flex substantially only in a transverse direction to that of the movement of said armature, and a damping medium for sa1d armature comprising printers roll composition 20. An electrical acoustical device com- 

